The present invention relates to methods for forming porous-surfaced polymeric bodies and particularly to such methods which use leachable foamed materials as the molding surface.
In the medical field, it has been suggested that it is advantageous for some applications to use implantable polymer-based devices having porous surfaces. For example, it has been suggested that vascular prostheses having porous surfaces on the inside aid in keeping blood clots on the surface of the vascular prosthesis and reduce the chances of having the clots break off the vascular wall, enter the bloodstream, and embolize to various parts of the body. It has also been suggested that having a porous outer surface on mammary prostheses reduces the chances of capsular contracture.
U.S. Pat. Nos. 4,604,762 and 4,459,252 disclose methods for forming porous-surfaced prostheses by mixing salt particles or other water-elutable material in with a polymeric composition, allowing the composition to harden, and removing the water-elutable material by leaching with water.
U.S. Pat. No. 4,199,864 discloses a method of fabricating a plastic implant having a porous surface by coating a mold interior with a release agent, sprinkling a layer of water-soluble crystals on the coated surface, adding an acrylic polymer and monomer mixture to fill the mold, heat curing the mixture, and, subsequently, removing the water soluble crystals by leaching.
U.S. Pat. No. 3,700,380 discloses a method of forming blood handling prostheses containing microcavities by applying fibrous, particulate or granular material (such as Nylon, DACRON, or acetate) to the surface which is to contain microcavities, while the surface is soft, causing the surface to set up, and thereafter using a solvent which dissolves the particles.
U.S. Pat. No. 3,899,556 discloses a method of producing porous ceramic prostheses using a framework prepared by partially dissolved and bonded together polystyrene particles with acetone, filling the framework with casting mass and disintegrating the framework with heat.
U.S. Pat. No. 3,090,094 discloses a method of making porous ceramic articles by immersing an open-celled porous element of pliable synthetic or natural organic material in a slurry of ceramic powder and binder, and, subsequently, firing the coated element to vaporize and burn out the porous element. U.S. Pat. No. 3,097,930 discloses a similar method for making a porous refractory material using a sponge, e.g. of polystyrene.
U.S. Pat. No. 2,996,389 discloses a method of making porous ceramic products by mixing bodies of blown or foamed plastic, such as polystyrene, with raw materials used to make ceramics, and, subsequently, volatilizing the plastic material by burning the finished product. Similarly, U.S. Pat. No. 3,176,054 discloses a similar method for making insulating refractories using hollow, spherical, expanded rigid plastic, e.g. polystyrene, beads.